1. Field of the Invention
The present invention relates to telecommunication networks and, more particularly, to a method and system for routing calls directed to wireless directory numbers in a telecommunications network.
2. Background of the Art
In the present telecommunications networks, a wireline telephone number or directory number (DN) is associated with a fixed geographic location and is served by a single wireline switch. A wireless DN, however, is associated with multiple geographic locations and is served by any one of a number of wireless switches depending on the specific geographic location of the associated wireless device at the time a call is made. This portability of a wireless DN is one of the basic attributes of wireless telephony.
A pair of home location register and visited location register in a telecommunications network provide seamless roaming when a call is placed to or from a wireless DN. A home location register is associated with a home wireless switch where a wireless DN resides (i.e., the wireless switch to which all incoming calls to the wireless DN are directed). A wireless device is located within its home area when the wireless device can directly communicate with its associated home wireless switch (i.e., located in the area covered by the home wireless switch).
A visitor location register is associated with a wireless switch currently serving a wireless device that is outside of its home area. A wireless device is outside of its home area (or roams) when the wireless device cannot directly communicate with the home wireless switch and instead communicates with another wireless switch, which is referred to as a visited wireless switch.
One problem with the present telecommunication networks is that two connections must be established when a call is placed to a wireless DN whose associated wireless device is outside of its home area. In such instances, the telecommunications network first establishes a connection to the home wireless switch associated with the wireless DN. The home wireless switch then establishes a second connection to a visited wireless switch that currently serves the wireless DN.
As an illustration, FIG. 1 shows a block diagram of a conventional telecommunications network 100. Telecommunications network 100 comprises a wireline switch 110, a home wireless switch 120, a home location register 130, a signal transfer point (STP) 135, a visitor location register 140, a visited wireless switch 150, a wireline telephone 155, antenna 170, and a wireless device 175.
Typically, a wireline subscriber using telephone 155 initiates a call request 180a by dialing the wireless DN associated with wireless device 175. When wireline switch 110 receives call request 180a, wireline switch 110 establishes a first connection 180b via a Public Switched Telephone Network (PSTN) 160 to home wireless switch 120, which is the home switch associated with the dialed DN.
Home wireless switch 120 sends an xe2x80x9cInterim Standard 41xe2x80x9d (IS-41) route_request message 180c to its associated home location register 130, requesting the current location of wireless device. The IS-41 standard is described in xe2x80x9cRadio Telecommunications Intersystem Operations,xe2x80x9d ANSI/TIA/EIA/41-D-1997, which is incorporated herein by reference. The IS-41 standard describes the communication protocol between home wireless switch 120, home location register 130, visitor location register 140, and visited wireless switch in telecommunications network 100.
If wireless device is outside of its home area as shown in FIG. 1, home location register 130 then identifies the visitor location register with which wireless device 175 last registered, for example visitor location register 140, and sends an IS-41 route_request message 180d via STP 135 to visitor location register 140.
Visitor location register 140 forwards route_request message 180d to its associated visited wireless switch 150, requesting a route to wireless device 175. Visited wireless switch 150 computes a temporary local directory number (TLDN), which can be used in establishing incoming calls to wireless device 175. Visited wireless switch 150 then returns the TLDN to visitor location register 140 in an IS-41 message 180e. Visitor location register 150 then sends via STP 135 to home location register 130 an IS-41 route_request_response message 180f that includes the TLDN.
Home location register 130 forwards route_request_response message 180f to home wireless switch 120. Using the TLDN in route_request_response message 180f, home wireless switch 130 then establishes a second connection 180g to visited wireless switch 150, which sends a ring signal to wireless device 175. Thus, to establish a call between telephone 155 and wireless device 175 when wireless device 175 is outside of its home area, telecommunications network 100 must establish two separate connections 180b and 180g. 
It is therefore desirable to have a method and system for reducing the number of connections that must be established in a telecommunications network when connecting a call to a wireless device that is located outside of its home area.
Methods and systems consistent with the present invention establish a call to a wireless DN in a telecommunications network by identifying a signaling node associated with the wireless DN, determining, at the signaling node, a route that excludes the home node associated with the wireless DN when the associated wireless device is outside of its home area, and establishing a connection via the determined route to a visited node in the network that currently serves the wireless DN.
In one embodiment, a first node receives a call request directed to a wireless DN when the wireless device associated with the wireless DN is outside of its home area. The first node invokes a trigger that identifies a signaling node associated with the wireless DN and requests from the signaling node a route for establishing the call to the wireless DN. The signaling node then determines a route that does not include the home node associated with the wireless DN. The first node then establishes via the determined route a single connection to a visited node serving the wireless DN. Accordingly, the telecommunications network establishes the call to the wireless DN without establishing a connection to the home node.
This summary and the following description of the invention should not restrict the scope of the claimed invention. Both provide examples and explanations to enable others to practice the invention.